Evaluating the impact of explicit encoding instructions on verbal learning.

The Hebb repetition effect, in which memory improves for repeated compared to nonrepeated sequences, is a well-established phenomenon in memory research. Despite its broad practical and theoretical importance, the mechanisms underlying this phenomenon remain unclear. It has recently been suggested that explicit awareness, or foreknowledge of repetition, plays a critical role in sequence learning. Across five large-scale experiments, using a serial recall task, we tested this proposition by examining the influence of foreknowledge (informing participants whether each sequence is repeated or nonrepeated) on Hebb learning. We used both an open pool, where nonrepeated trials contained unique items, and a closed pool, where the same items were used on every trial. In Experiment 1, all participants received foreknowledge; half were assigned to the open-pool group and half to the closed-pool group. The pool-size effect persisted: Learning was stronger in open than in closed pools. Experiment 2 compared foreknowledge and no foreknowledge groups using an open pool and found no benefit of foreknowledge. In Experiments 3, 4, and 5, using closed pools, foreknowledge provided a modest advantage for Hebb learning, especially for nonwords (Experiment 4) compared to words (Experiments 3 and 5). Experiment 5 further compared learning based on recognition of the repeated sequence postexperiment and revealed that learning only occurred when the repeated sequence could be recognized, regardless of the foreknowledge condition. Together, these findings suggest that while foreknowledge of repetition can enhance sequence learning under conditions of high interference, it is not a sufficient condition for learning to occur. (PsycInfo Database Record (c) 2026 APA, all rights reserved).